Create `py.typed` for launch
Add py.typed so downstream users can use type hints.
Pulls: ros2/launch#828 Gist: https://gist.githubusercontent.com/christophebedard/db364753930df4b0d5737273246841da/raw/9a59475aeb13788224eaf48e1b763839f662ff96/ros2.repos BUILD args: --packages-above-and-dependencies launch TEST args: --packages-above launch ROS Distro: rolling Job: ci_launcher ci_launcher ran: https://ci.ros2.org/job/ci_launcher/15196
@christophebedard Since the Windows failures seem unrelated, would it be alright to merge in?
Indeed, I can find the same failure in similar tests for another package in a different job: https://ci.ros2.org/job/ci_windows/23336/testReport/junit/ament_mypy.test/test_xmllint/test_xmllint/